1. Field of the Invention
The present invention generally relates to the use of Mobile Internet Protocol (“IP”) systems, methods and protocols in PCS systems and, more particularly, to a method for dynamically allocating IP addresses for time sensitive hosts based on priorities and guard bands.
2. Description of the Related Art
With the proliferation of wireless cellular devices (mobile stations), an increasing need has arisen for a methodology and system to provide seamless mobile access to the Internet via existing personal communication services (PCS) networks. To meet this need, the wireless access system must support high-speed packet data transmissions and must also efficiently communicate with the Internet backbone. While emerging PCS technologies, such as CDMA2000 and Wideband CDMA (WCDMA), define packet data transmission over the air interface, none of these systems present a flexible architecture for connecting a wireless access system to the Internet backbone which is also suitable for general mobile IP interconnectivity.
FIG. 1 is an illustration of a conventional cellular system network 10. The network 10 includes a mobile switching center (MSC) 12 connected to one or more base station controllers (BSC) 14. Each BSC 14 controls one or more base stations (BS) 16 which provide wireless communication links to various mobile stations (MS) 18. The MSC 12 interfaces to a public switched telephone network (PSTN) 20 for routing the voice calls and to a separate signaling system 22 for signaling used for PCS mobility management. Such a conventional cellular system provides Internet access through voiceband modems in the mobile stations, which connect to an Internet access server (not shown) interfaced to the MSC 12, either directly or via the PSTN 20. Alternatively, an interworking function (IWF) 24 interfaced directly to the MSC provides the interworking of protocols between the air interface and the Internet.
Although conventional cellular systems provide adequate data and voice service in some circumstances, such network configurations suffers from several deficiencies. In particular, the connection model is based on dialup modems where the IWF acts as a server, providing a point-to-point connection to the MS and assigning a temporary IP address to the MS that is valid only during the session. When the MS changes the point of attachment with the Internet (i.e., a hand off is performed), a new session must be established and a new temporary address must be assigned to the MS using an address assignment scheme. Therefore, an Internet session cannot be maintained as the MS changes the point of attachment.
As the MS moves across different subnets, packet delivery to the MS is based on the temporary IP address and not the static IP address of the MS. Since the MS does not have a static IP address, datagrams cannot be delivered to the MS until the MS has established a Point-to-Point Protocol (PPP) session and the host attempting to send data knows the temporary IP address of the MS.
The advent of wireless IP networks has presented challenging problems in the area of dynamic IP address allocation. Wireless IP networks comprise a plurality of network cells wherein a plurality of handoff and resident hosts communicate with the wireless IP network. Handoff hosts are network hosts whose initial network connection was established in another cell and that subsequently migrate to a new network cell. In contrast, resident hosts are hosts whose initial network connection was established in the present cell and that have not migrated to another network cell. Each network cell further includes a base station that maintains handoff and resident host network connections within the network cell, and facilitates dynamic handoff of handoff hosts within its cell.
The base station within each cell facilitates a network connection with its handoff and resident users through IP addresses assigned to the network hosts within the cell. Thus, an IP address must be allocated to the handoff and resident hosts within a cell to establish and maintain a network connection. The IP addresses dedicated to the handoff and resident hosts can be allocated by methods including an IP address server system(s) that assigns IP addresses for new hosts, and base stations themselves that may determine their own necessary IP address allocation. IP address servers that allocate IP addresses can include servers that are part of a base station itself, or can include IP address servers that are attached to the network and send IP address allocations to the base station within a cell. These IP address allocation methods and apparatuses confront a number of problems when allocating IP addresses to handoff and resident hosts within their cells.
First, whenever a host initially establishes a network connection within a cell, the host is considered a resident host, because it establishes its initial network connection within the cell. In order for the resident host to establish its network connection, a base station within the cell must allocate an IP address from the cell's IP address pool to the resident host. In contrast, whenever a resident host migrates to a new cell after already having its network connection in a prior cell, the host becomes a handoff host, and the new cell must maintain the preexisting network connection of the handoff host. If the new cell has a different IP subnet address relative to the prior cell, the new cell must allocate a new IP address to the handoff host in order to maintain the handoff host's network connection from the prior cell.
Current dynamic IP address allocation protocols such as Dynamic Host Configuration Protocol (DHCP) treat resident and handoff hosts as equivalent and without preference when allocating IP addresses to these hosts. Thus, a base station may allocate an IP address to a resident host instead of a handoff host, thereby permitting a new resident network connection in place of the prior network connection of a handoff host network, which must be dropped. This equal treatment is obviously undesirable, because denying a resident host an IP address will merely prevent a new network connection, whereas denying a handoff host an IP address causes its preexisting network connection to be terminated. Thus, IP address allocations to handoff hosts should be preferred to IP address allocations of resident hosts in order to facilitate the handoff of preexisting handoff host network connections.
Second, the problem of handoff and resident host network access is further aggravated due to the fact that there is no minimum number of IP addresses that are reserved by individual cells to ensure a certain level of host access. The minimum number of IP addresses available will vary from cell to cell, and thus handoff and resident hosts will have differing degrees of access to the IP network based on the particular cell wherein the host is communicating with the network. As a result, fair access to the wireless IP network for handoff and resident hosts differs from cell to cell, because one cell may have significantly fewer IP addresses to allocate relative to another cell. This is another limitation of present IP address allocation protocols, because it is desirable to ensure fair access of handoff and resident hosts to the network regardless of the particular cell wherein these hosts reside.
In sum, present dynamic IP address allocation protocols for wireless IP network systems suffer from two significant problems. First, these protocols treat resident and handoff hosts equally when allocating IP addresses, thereby causing preexisting handoff host network connections to be dropped in favor of new resident host network connections, when it is preferable to preserve a preexisting handoff host network connection by denying a new resident host network connection. Second, there is no minimum number of IP addresses allocated to individual cells, thereby causing fair access problems when different cells provide different numbers of IP addresses for handoff and resident hosts, thereby making network access arbitrarily dependent on the cell in which the handoff and network host reside.
New Internet Protocol(IP) based wireless networks are emerging. These emerging networks use IP protocols for transport and control of data and/or voice traffic which is transmitted over wireless and/or wired networks. IP Version 4 (IPv4) is the IP implementation standard which is in widespread use for such transmissions. With the increasing number of electronic devices, such as cell phones, personal digital assistants (PDAs) and handheld computers, which are becoming IP enabled, IPv4 can experience a shortage of addresses for assignment to each device. As a result, care must be taken to utilize address allocation schemes which ensure that a sufficient number of address space is reserved for assignment to each networked device.
IP version 6 (IPv6) is the next-generation IP protocol implementation standard. This standard possesses a significantly expanded address space to accommodate the ever expanding range of networked devices. The addressing scheme utilized in IPv6 is not expected to experience the address exhaustion associated with IPv4, and therefore address allocation schemes using IPv6 do not need to limit the number of addresses for assignment to each network device.
However, with the growing popularity of wireless communications and time sensitive communication sessions, the speed of address assignment, as opposed to the number of available addresses, has become the main detractor from achieving optimal network performance. Here, handoff hosts may be forced to experience unacceptable latencies in acquiring IP addresses. These latencies have a negative effect on application performance, and may cause the communication session to abort. Moreover, the rapid growth of wireline and wireless user populations has escalated the traffic experienced at IP address servers. With such an increase in the number of requests being handled at a server, the average service time per request increases. These increased service times increase the potential for users with time sensitive constraints to experience degraded network performances. Therefore, it is incumbent upon current address allocation schemes to distribute addresses for wireless and mobile users expediently such that address acquisition latencies do not occur.
IP hosts served by a new cell may belong to a different IP subnet. As a result, when wireless mobile hosts in an IP-based wireless network move into new cells, they are often required to update (change) their IP addresses. Furthermore, wireless and wireline IP hosts may share the same IP network and, consequently, will compete for the same pool of IP addresses. In IPv4 this competition for IP addresses can cause “address exhaustion,” and therefore a judicious assignment of address space is important.
Accordingly, it is apparent that there is a need and desire for a method for dynamically allocating IP addresses to wireless and wireline IP hosts which share the same pool of IP addresses in a network such that time sensitive handoff hosts will possess a higher probability of obtaining a new IP address in a timely manner, and such that the probability of degraded network performance due to delays in the assignment of IP addresses to wireless hosts is reduced.